Generally, an electronic copying apparatus has a developing device within its housing. A developing agent is supplied from the developing device to an electrostatic latent image formed on a photosensitive drum, and the latent image is thereby developed. However, electronic copying apparatuses provided with a plurality of developing devices have recently been developed. In copying apparatuses of this type, the developing devices are opposed, alternatively, to a photosensitive drum, and supply the drum with developing agents of different colors for multicolor developing.
These prior art copying apparatuses, however, require a sophisticated selecting mechanism for alternatively opposing the developing devices to the photosensitive drum, resulting in increased size and higher cost.